Re: insulation testing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terrell W. Fritz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <terrellf-at-qwest-dot-net>

Hi Rick,

There are all kinds of commercial hi-pot and insulation testers.  I have a
Bertan 50kV DC power supply that can monitor current down to a micro amp.  That
is 50 gigaohms at 50kV :-))  Don't be too put off by "pro" equipment since it
sells surplus for pennies on the dollar...  Companies spend 100's of thousands
on equipment one day that turns into excess inventory worth its weight in scrap
the next day...  The corporate accountants (cubical next to Dilbert's) can
explain how companies can do that and still make money...

People have used Tesla coils for insulation testing too but the high frequency
and arcs are sort of "too wild" and the thing is not super scientific.

For 60Hz, a 15kV NST and an AC microammeter could be very useful.  You may want
a "cheap" meter or one with some heavy added protection in case something
breaks down.  I would suggest simple Styrofoam or any large cell foam plastic
for insulation (it's electrical properties are close to air).  The meter and
such needs to be real well insulated.  If you use just one side of the NST it
could be kept near the ground side so the meter does not float at high voltage.

Cheers,

        Terry


At 12:11 PM 3/30/2002 -0700, you wrote:
>Original poster: "PotLuck by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><potluck-at-xmission-dot-com>
>
>Hi List,
>Has anyone done home insulation testing? I'm primarily interested in whether a
>material will "hold off" a certain voltage or not. I see on the net in
>commercial testing such tests for power factor tests, power losses and
>monitoring of currents in the uA area. These of course are important
properties
>of a material but may be a little too in-depth for home testing and the
>properties I'm looking for. 
> 
>The voltages I'm interested in looking at are in the range of ~7.5Kv at 60Hz,
>not in the RF range inherent in normal tesla coil operations.
> 
>Any suggestions as to an "apparatus" that can be made easily? I have various
>NSTs, variacs and transformer oil at hand along with a scope and several
>multimeters.
> 
>Simply using a two electrodes with the material in question placed between
them
>(not under oil) sometimes produced a purple haze or what appears to be a
>corona. Allowing the test to run for several minutes with the corona didn't
>appear to form any holes in the material, not by the naked eye anyway, and
>there was no burning. I've looked at mylar, polypropylene and HDPE.
> 
>Mylar film (adhesive backed) from McMaster-Carr has a dielectric strength
rated
>at 7500 V/mil. with 4mils placed between the electrodes "corona" developed at
>about 4000 volts but no damage to the mylar was apparent. Again this was not
>under oil.
> 
>But what is it I'm looking for? Lack of corona? Corona can't be good.
> 
>I'm relatively new to the high voltage arena so and advice in this area would
>be greatly appreciated since insulation is a big part of coiling.
> 
>Thanks in advance! :)
> 
>Rick W.
>SLC  
>
>
>